This invention relates to a method of recovery of excess gas energy for furnace gas energy recovering plants for recovering the energy of furnace gas from one or a plurality of blast furnaces through an expansion turbine mounted in each exhaust gas system of each blast furnace.
Heretofore, a furnace gas energy recovering plant comprises an expansion turbine mounted in the exhaust system of a blast furnace for recovering the energy possessed by furnace gas by converting same into electric power. In this case, an attempt is made to introduce as much gas as possible to the expansion turbine to maximize the volume of recovered gas.
However, as the blast furnace shows a change in the pattern of its operation and the volume of furnace gas produced increases, it is impossible to handle all the gas by the available expansion turbine. Thus it has hitherto been usual practice to pass excess gas through a septum valve for adjusting furnace gas pressure, to release same to outside without recovering.
Particularly in an iron foundary having a plurality of blast furnaces, the present tendency is that it is impossible to neglect the total volume of excess gas from these blast furnaces. The gas flowing through the septum valve produces a large amount of noise, making it necessary to provide measures to cope with the situation. When the blast furnaces slow down their operations, reserve is provided to the energy recovering ability of the foundary. Thus the blast furnaces tend to become unbalanced in the production of furnace gas.